This invention relates to the art of storage reels for wire and, more particularly, to an improved storage reel of wood material for protectively storing a continuous length of electric arc welding electrode wire.
The present invention finds particular utility in the protective storage of a continuous length of electric arc welding electrode wire comprising an iron core and an outer coating of copper. Such electrode wire is sometime subject to discoloration during storage on a wood reel apparently as the result of moisture in the wood material, the temperature of the wire when initially wound onto the reel and/or the decomposition of glues used in the manufacture of the wood materials from which the reels are constructed. Accordingly, the invention will be disclosed and described in detail herein in connection with such electrode wire. At the same time, however, it will be appreciated that the invention is applicable in general to the protective storage of continuous lengths of other electric arc welding electrode wire wherein the material of the electrode is subject to color degradation while stored on a reel of wood material.
As is well known in the art of continuous electric arc welding, a continuous length of welding electrode wire is wound onto a storage reel and is fed therefrom to the point of welding by an appropriate feeding mechanism which progressively unwinds the wire from the storage reel. Often, the storage reel is constructed from wood material such as plywood or bonded and pressure formed boards of aligned wood fiber. Generally, the reels are constructed by assembling a tubular core and end flanges, whereby the reel is in the form of an outwardly open channel for confining the welding wire wound thereon. In one particular reel construction, the flanges are provided with annular recesses to receive the ends of the tubular core and, to facilitate the ease of assembly, the side of the recess adjacent the radially outer surface of the core is chamfered. This provides a grooved area at the juncture between the flanges and core and, in winding the electrode wire thereon, the initial convolutions of the wire are pushed into the grooved area and bind to the extent that they will not freely unwind from the reel during a welding operation. Accordingly, such binding results in the loss of a considerable length of the welding wire.
Discoloration of electric arc welding electrode wire having an iron core and an outer coating of copper was discovered in connection with the storage of such electrode wire on reels made from wood materials of the foregoing character. More particularly, pronounced discoloration of the electrode wire appeared in the convolutions of the wire adjacent the flanges of the reels, such discoloration of the copper coating being blue-black and thus far from the normal sheen of copper. In this respect, in manufacturing the copper coated, iron wire the wire is drawn through drawing dies and immediately wound on the reel upon exiting the last die, and the drawing results in the copper coating having a shinny, bright appearance. The manufacturing process for the coated wire also results in minute interruptions in the copper coating through which the iron core is exposed and thus subject to oxidation. While such discoloration of the welding wire does not affect the quality of a weld made with the wire, users of the wire are sometime not willing to risk product quality and, thus, a reel of electrode wire on which a portion of the wire is discolored may be commercially unacceptable although it is perfectly acceptable for the intended welding function. While the discoloration is only present on those portions of the electrode wire adjacent the reel flanges, if such discoloration renders the electrode wire cosmetically unacceptable to the customer, the entire reel of wire is wasted.
Initially, it was thought that the discoloration of the coated wire was the result of excessive moisture in the wood material from which the reels are constructed. In pursuing the problem in this respect, it was discovered that pre-drying of the wood material of the reels to a moisture content below 3% substantially eliminated the discoloration and rusting problem. However, depending upon the time of storage and the humidity and temperature conditions in the environment of storage, the wood material of the reels would on occasion absorb moisture, whereby discoloration would occur. Furthermore, the process of manufacturing the copper coated iron welding electrode wire results in a high temperature of the coated wire exiting from the last drawing die and being wound on the wooden reels. The high temperature of the wire resulted in substantially immediate discoloration of the welding wire on reels constructed from pre-dried wood. If moisture was the only cause for discoloration, as previously thought, it was not understood why the increase in the temperature of the wire being wound on the reel would cause substantially immediate discoloration, and it was believed therefore that the discoloration problem was the result of more than just the moisture content of the wood material of the reels.
In pursuing the problem, it was discovered that the water soluble Urea formaldehyde glues used in the production of plywood, and pressed particle and fiberboard, decompose in the presence of moisture and heat to form ammonia compounds and formaldehyde. The ammonia compounds turn the copper coating on the wire blue-black, and the formaldehyde oxidizes or rusts exposed portions of the iron core of the wire. Furthermore, glue fillers used in conjunction with filling knot holes and the like in plywood contain free aldehydes which also oxidize or rust the iron core. Since the discoloration problem increases as the moisture content in the wood material increases, even if the electrode wire stored on the reel is cold, it was realized that the predrying of the wood materials from which the storage reels are made, and winding the wire thereon after cooling, would not only be undesirable from the standpoint of manufacturing the wire but, also, would not resolve the discoloration problem. Consequently, oxidation or electrochemical corrosion of the welding wire was undesirable, but was hereto difficult to prevent when using somewhat inexpensive wooden reels.